Mesh Grabber is probably the easiest but least accurate as it's not really sculpting.
Zbrush is the industry standard sculpting tool and with Daz bridge is the most convenient, but costs $.
Blender is free but getting your char from and to Daz is the most time involved out of the three.
Between Blender and Zbrush, how good your results will be is based entirely on your ablility to sculpt the ass grabbing deformation. If you sail the high seas, I'd recommend going the Zbrush route and spending a day wrapping your mind around the alien UI. It's worth it in the long run though and you'll also be able to sculpt new custom morphs for your chars rather than solely relying on Daz morph libraries.